Isocyanide Palladium Research Articles

Molecular Switching through Chalcogen-Bond-Induced Isomerization of Binuclear (Diaminocarbene)PdII Complexes

Binuclear diaminocarbene complexes, which form as a regioisomer mixture in the reaction between isocyanide–palladium(II) complex cis-[PdCl2(CNXyl)2] and 1,3-thiazol-2-amine, are able to exchange an anionic chloride ligand with other halides, such as Br or I. This process also affords binuclear complexes as mixtures of kinetically and thermodynamically controlled regioisomers. In CDCl3 solutions, we observed interconversion of kinetically and thermodynamically controlled regioisomers. The results of the DFT calculations revealed that in CHCl3 solution, each pair of the isomers exhibited two different types of chalcogen bonding such as S···X or S···N; the presence of CBs for two complexes in the solid state was also proven through X-ray crystallographic study. Based on the combined experimental and theoretical data, it could be concluded that thermodynamic favorability for the formation of thermodynamically controlled regioisomers increases in the Cl < Br ≈ I row and correlate well with the energy difference between S···N and S···X (X = Cl, Br, I) chalcogen bonds in kinetically and thermodynamically controlled products. This means that it is possible to change the structure of metallocycles in binuclear diaminocarbene complexes by simply replacing one halide ligand with another.

Catalysis of the Suzuki reaction by acyclic diaminocarbene palladium complexes generated in situ

Acyclic diaminocarbene palladium complexes generated in situ by nucleophilic attack of morpholine, 4-nitrophenylhydrazine, or benzhydrazide on bis(isocyanide) palladium(II) complexes catalyzed the Suzuki reaction of 4-iodo- or 4-bromoanisole with phenylboronic acid. Morpholine turned out to be the best catalyst modifier. The cross coupling reaction under fairly mild conditions (reflux in ethanol in the presence of potassium carbonate) in 2 h afforded 4-methoxybiphenyl whose yield was insignificantly lower than in the presence of preliminarily prepared catalyst. Neither preliminary degassing nor protection from atmospheric moisture and oxygen was necessary.

ChemInform Abstract: Structure of Isocyanide Palladium(II) Complexes and Their Reactivity Toward Nitrogen Nucleophiles

AbstractReview: 88 refs.

Structure of isocyanide palladium(II) complexes and their reactivity toward nitrogen nucleophiles

The review generalizes published data on the chemistry of palladium(II) complexes with isocyanides. The structure and specific features of the reactivity of isocyanide palladium(II) complexes with mono- and polynitrogen nucleophiles, as well as the structure of the products of these transformations, are discussed.

New acyclic aminocarbene palladium(ii) complexes as convenient catalysts for the Sonogashira and Suzuki cross-coupling

A reaction of isocyanide complex cis-[PdCl2(CNAr)2] with hydrazones H2N-N=CR1R2 proceeded at the carbon atom of one of the isocyanide groups and gave the corresponding diaminocarbene isocyanide palladium(ii) complexes. These complexes showed high catalytic activity in the Sonogashira and Suzuki cross-coupling reactions.

Chiral linear isocyanide palladium(ii) and gold(i) complexes as ferroelectric liquid crystals

A. Omenat, J. Serrano, T. Sierra, D. B. Amabilino, M. Minguet, E. Ramos and J. Veciana, J. Mater. Chem., 1999, 9, 2301 DOI: 10.1039/A903084K

Bis(cyclohexyl isocyanide)palladium(II) Halides and Their Benzene Complexes

Abstract Bis(cyclohexyl isocyanide)palladium(II) chloride, PdCl2(C6H11NC)2 (1) was prepared from PdCl2. The configuration of the complex 1 is cis with respect to the isocyanides. The isocyano group in one cyclohexyl isocyanide takes axial conformation to chair form cyclohexyl group, while another takes equatorial conformation. By recrystallization of 1 from benzene bis(cyclohexyl isocyanide)palladium(II) chloride-benzene, PdCl2(C6H11NC)2(C6H6)2 (2) was prepared. IR spectrum of 2 shows a characteristic absorption at 700 cm−1 which is due to the benzene incorporated in the complex. Similar benzene complex was also prepared from PdBr2.

Cyclic Carbene–Palladium(II) Complexes Derived from the Reactions of Isocyanide–Palladium(II) Complexes with Nitrilimines and Nitrilylides

Abstract cis-[PdCl2(PPh2R1)(CN–C6H4–CH3-p)] (R1=Ph or Et) reacts with nitrilimines or nitrilylides, derived from the reactions of either N-phenylarenecarbohydrazonoyl chlorides or N-(p-nitrobenzyl)arenecarboximidoyl chlorides with triethylamine, to afford novel cyclic carbene–palladium(II) complexes, viz. 1,2,4-triazol-5(4H)-ylideneor 2-imidazolin-5-ylidenepalladium(II) ones, respectively. Halogen exchange reactions of the carbene complexes with lithium bromide or sodium iodide give the corresponding dibromo- or diiodocarbene complexes, respectively. trans-[PdI2(PPh2-C6H4-CH3-p)(CN-C6H4–NO2-p)] also reacts with the nitrilimine or the nitrilylide to produce cyclic carbene–palladium(II) complexes. All the complexes prepared in this study are characterized by elemental analysis, IR and 1H-NMR.

A Wittig-type Reaction of Phosphoranes with Carbon Monoxide Coordinated to Palladium. A Synthetic Route to Isocyanide Palladium Complexes

Abstract The reaction of carbon monoxide with triphenyl(phenylimino)phosphorane proceeded at room temperature in the coordination sphere of palladium to give a mixture of phenyl isocyanide and carbonyl complexes of palladium. Triphenyl (t-butylimino)phosphorane gave bis(t-butyl isocyanide)palladium chloride in a low yield. Benzophenone triphenylphosphazine and triphenyl(p-tolylsulfonylimino)phosphorane failed to react with carbon monoxide.

Reactions of dimethyl- and diphenyl-mercury with dihalobis(isocyanide)palladium(II) complexes

The reaction of cis-[PdCl 2(CNR) 2] (R = Ph, p-MeC 6H 4, p-MeOC 6H 4) and trans-[PdI 2(CNPh) 2] with HgR′ 2 (R′ = Me, Ph) followed by addition of PPh 3 (Pd/PPh 3, 1 2 ) gives complexes of the type trans- [PdX {C(=NR)C(R′)=NR}(PPh 3) 2] (X = Cl, I) I as main products. These bis(imino) compounds may result from double insertion of the coordinated isocyanides into a PdR′ σ-bond. NaBPh 4 was also found to act like HgPh 2 as a good phenylating agent towards coordinated isocyanide. The reactions of I with methanolic HClO 4 yield cationic compounds: trans- [PdX{C(NHR)C(R′)=NR}(PPh 3) 2]ClO 4; the protonated bis(imino) group may also be formulated as {C(=NR)C(R′)NHR} and a fast equilibrium between the two forms probably exists in solution. The factors influencing the reaction with HgR′ 2 and spectroscopic data (IR and 1H NMR) for the complexes are reported and discussed.